1. Field of the Invention
The present invention relates to a focus adjustment apparatus used for image capturing apparatuses, such as still cameras, video cameras, or various observation apparatuses.
2. Description of the Related Art
Conventionally, for performing automatic focus (AF) in a camera, a focus detection apparatus with a so-called phase difference detection method is known. In the phase difference detection method, a light flux from an object, having passed through different exit pupil regions of a photographic lens, is caused to form an optical image on each of a pair of line sensors, and photoelectrically converted into a pair of object images. Thereafter, based on the object images, an amount of displacement between relative positions of the pair of object images is calculated (hereinafter, referred to as phase difference calculation). To perform autofocus, the photographic lens is driven based on the defocus amount obtained by the phase difference calculation. In the focus detection apparatus of this type, line sensors are arranged at positions corresponding to each of a plurality of AF frames (focus points). An example of this technique is discussed in Japanese Patent Application Laid-Open No. 2011-232544.
In recent years, for the purpose of an enhancement of AF performance, the number of AF frames has been increased. When the number of AF frames is increased, owing to restriction of an optical layout, a plurality of AF frames may be arranged in high density with respect to a pair of line sensors. In this case, a plurality of AF frames corresponding to the line sensors with which the focus control has been performed will be displayed. However, the focusing result for an object is obtained in which an AF frame, among the plurality of AF frames, cannot be displayed to inform the user of the AF state. As a result, whether optimum focus is achieved on a user's intended target may not be known by display.